Chairs and sitting devices have been subject to constant efforts to improve the ease, comfort, style or cost of the way people sit. With the advent of the age of plastics, additional options became available for low cost or portable chairs that could be injection-molded into a variety of shapes and sizes. As plastics can be made quite flexible and elastic, the chairs could also be designed to provide an additional measure of structural flexibility, and therefore comfort, than could be provided with seat platforms or sitting surfaces made from more rigid materials, such as wood, metal, ceramics, etc.
Simple plastic chairs have material limitations, however, which include the permanent deformation and damage that can result from excess loads. It has been discovered that in order to make chairs from flexible materials, such as plastic, thin metal sheets, etc., elasticity and strength are generally inversely proportional. In other words, the flexible characteristics desired for improved comfort must often be sacrificed to maintain sufficient strength to accommodate anticipated abuse and overload conditions without experiencing permanent damage.